An intellisense feature would be cool, I agree. In the meantime, may I suggest this:
http://www.msgpluslive.net/scripts/view/335-Plus!...alltips-for-SciTE/ .
As for "Live Error Checking", it's not been done but the next version allows seeing debug traces directly inside the editor and when an error occurs, you now get a link directing you to the fauly line.